Process for fabricating a crack resistant resin encapsulated semiconductor chip package

ABSTRACT

A heat-resistant adhesive is provided for use in an adhesive member for the fabrication of a semiconductor package by bonding a semiconductor chip to a lead frame with the adhesive member and sealing at least the semiconductor chip and a bonded part between the semiconductor chip and the lead frame with a sealant. The adhesive has a coming-out length of not more than 2 mm and a water absorption rate of not more than 3 wt. %. Preferably, the adhesive has a glass transition point of at least 200° C.

This is a continuation application under 37 C.F.R. 1.53(b)(1) of priorapplication Ser. No. 09/044,575, filed Mar. 19, 1998 now U.S. Pat. No.6,046,072, which is a continuation application of application Ser. No.08/542,576, filed Oct. 13, 1995, which is a continuation-in-part ofapplication Ser. No. 08/514,353 filed Jul. 27, 1995, now abandoned,which is a FWC of application Ser. No. 08/218,544, filed Mar. 28, 1994,now abandoned.

This application is a continuation-in-part of co-pending U.S.application Ser. No. 08/514,353 filed on Jul. 27, 1995, entitled“HEAT-RESISTANT ADHESIVE” which is a Continuation Application underC.F.R. § 1.62 for U.S. application Ser. No. 08/218,544 filed on Mar. 28,1994.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a heat-resistant adhesive especially suitablefor the bonding of a semiconductor chip to a lead frame and an adhesivemember using the adhesive.

More particularly, this invention relates to a heat-resistant adhesivesuitable for use in a semiconductor package, especially a package of LOC(lead on chip) structure, which is capable of preventing or minimizingthe occurrence of cracks when solder is subjected to reflow when thepackage has absorbed moisture.

2. Description of the Related Art

The semiconductor package is fabricated by connecting a lead frame to asemiconductor chip using an adhesive or resonance solder andelectrically connecting electrodes of the chip to the lead frame,followed by sealing the entire structure into a molded form asillustrated in FIGS. 1 thru 3.

In general, a conventional package has a structure as shown in FIG. 3where the chip is mounted on a tab (die pad) of the lead frame. Theconnection between the lead frame and the chip is made by Au—Siresonance solder or a thermosetting epoxy adhesive (a die bondingagent).

However, as the integration degree of in the package has become higherand a size of a chip to be mounted therein has become larger, thepercentage of the volume occupied by the chip has become higher to suchan extent that the chip cannot completely be encased in a structure asshown in FIG. 3 where the chip is mounted on the tab of the lead frame.To solve this problem, a package having no tab such as shown in FIG. 1or FIG. 2 has been proposed, for example, in U.S. Pat. No. 5,140,404,Japanese Patent Application Publications (KOKAI) 61-218139 and61-241959, U.S. Pat. No. 4,862,245, and Japanese Patent ApplicationPublications (KOKAI) 2-36542 and 4-318962. The package structures ofFIGS. 1 and 2 are called LOC (lead on chip) and COL (chip on lead),respectively. In these packages, the connection between the lead frameand the chip is made by a thermosetting adhesive or a heat-resistant hotmelt.

With the structures as shown in FIGS. 1 and 2, it is the trend that asthe package size is becoming smaller and thinner and the percentage ofthe occupation by the chip is becoming higher, the thickness of thesealing material is becoming thinner accordingly. Therefore, moistureabsorbed by the adhesive or the sealing material would more readilyoften cause cracks in the package when it evaporates or expands.

To solve this problem, some attempts to improve the sealing materialsand/or the adhesives employable for the package have been proposed. Forexample, with respect to the sealing materials, lowering of moistureabsorption and improvement of mechanical strength have been discussed(Japanese Patent Application Publication (KOKAI) 5-67703). With respectto the adhesives, it has been proposed to reduce the moisture absorptionor to divide an adhesive member into small pieces to promote escape ofvapor during reflow in the soldering (Japanese Patent ApplicationPublication (KOKAI) 3-109757). However, there have been no proposaldirected toward modifying the properties of the adhesive to be employedfor the LOC package.

There has been another attempt which intentionally allows a solvent toremain with a view to lowering a bonding temperature, lowering theviscosity of the resin (Japanese Patent Application Publication (KOKAI)3-64386) or allows a solvent to remain to improve the fluidity andincrease the adhesion to lower the possibility of a leak current betweeninner leads (Japanese Patent Application Publication (KOKAI) 2-36542).

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide anadhesive suitable for use in a semiconductor package, especially asemiconductor package of LOC structure, which is capable of preventingpossible cracks from occurring during reflow of solder when the packagehas absorbed moisture.

The inventors of the present invention has unexpectedly found, as aresult of their research the relationship between cracks developed inthe LOC package during reflow of the solder when package has absorbedmoisture and the properties of the adhesive employed. The inventors haveunexpectedly found that the fluidity or hardness of the adhesive at ahigh temperature has more impact on such package cracks than themoisture absorption or the glass transition point Tg of the adhesive.More particularly, they have found that an adhesive having a specifichardness or fluidity may advantageously be employed to prevent thepackage cracks in the LOC package. Thus, the present invention has beenachieved.

Heretofore, it has only been known that the solvent may be intentionallyleft in the adhesive with a view to lowering the bonding temperature tolower the viscosity of the resin (KOKAI 3-64386) or the solvent may beleft to enhance the fluidity and improve the adhesion for reducingcurrent leakage between the inner leads (KOKAI 2-36542). It has not beenknown before the present invention that the hardness or retardation ofthe flow of the adhesive is more influential on the package cracks thanthe moisture absorption or Tg of the adhesion and that the adhesivehaving the specific hardness or fluidity is surprisingly effective toimprove the resistance against the package cracks.

The present invention therefore provides:

(a) a heat-resistant adhesive suitable for use in an adhesive member forthe fabrication of a semiconductor package by bonding a semiconductorchip to a lead frame with the adhesive member and molding at least thesemiconductor chip and the bonded part between the semiconductor chipand the lead frame with a molding compound, in which the heat-resistantadhesive has a coming-out-length of not more than 2 mm and a waterabsorption rate of not more than 3 wt. %,

(b) a heat-resistant adhesive suitable for use in an adhesive member forthe fabrication of a semiconductor package by bonding a semiconductorchip to a lead frame with the adhesive member and molding at least thesemiconductor chip and the bonded part between the semiconductor chipand the lead frame with a molding compound, in which the heat-resistantadhesive has a coming-out length of not more than 2 mm, a waterabsorption rate of not more than 3 wt. % and a glass transitiontemperature of at least 200° C.,

(c) a heat-resistant adhesive, in which the adhesive member is acomposite adhesive sheet comprising a heat-resistant film and theheat-resistant adhesive applied in the form of a coating layer on onesurface or opposite surfaces of the heat-resistant film, and

(d) a heat-resistant adhesive, in which the adhesive member consists ofthe heat-resistant adhesive alone. The heat-resistant adhesivesaccording to the present invention have excellent package-crackresistance and are effective especially for the improvement of thereliability of semiconductor packages.

The term “water absorption rate” used herein means a water absorptionrate obtained from a change in weight of an adhesive before and afterimmersion in water. Here, a film of the adhesive having a size of 5 cm×5cm with a thickness of 25 μm is used as a testing object and, afterdried at 100° C. for 1 hour, it is immersed in water at 23° C. for 24hours to measure the water absoprtion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates a semiconductor package fabricated bybonding a semiconductor chip to a lead frame with an adhesive memberemploying the heat-resistant adhesive of the present invention and thenmolding the semiconductor chip and the bonded part between thesemiconductor chip and the lead frame with a molding compound, in whichthe semiconductor chip is located below the lead frame;

FIG. 2 schematically illustrates a semiconductor package similar to thatof FIG. 1 except that a semiconductor chip is located above a leadframe; and

FIG. 3 schematically illustrates a semiconductor package similar to thatof FIG. 1 except that a semiconductor chip is located above a leadframe.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will hereinafter be described in detail.

No particular limitation is imposed on the specific heat-resistantadhesive employed in the present invention insofar as its waterabsorption rate and coming-out length are not more than 3 wt. % and notmore than 2 mm. Among preferred heat-resistant adhesives are those witha principal constituent of a heat-resistant thermoplastic resin,preferably having a glass transition temperature of at least 200° C. Forthese reasons, a polyimide adhesive or a polyamide adhesive ispreferred.

The term “polyimide” as used herein should be construed as embracingresins containing imide groups, such as polyamide-imides,polyester-imides, polyether-imides and polyimide.

The water absorption rate of the heat-resistant adhesive according tothe present invention is 3 wt. % or less, preferably 2.5 wt. % or less,more preferably 2.0 wt. % or less. Its coming-out length is 2 mm orless, preferably 1 mm or less, more preferably 0.5 mm or less. Inparticular, the heat-resistant adhesive according to the presentinvention desirably has, in addition to the properties described above,a glass transition temperature of east 200° C., preferably 225° C. orhigher, more preferably 250° C. or higher.

The term “coming-out length” as used herein means the length of acame-out peripheral portion of a 19×50 mm wide adhesive film of 25 μm inthickness as measured at a central part in the direction of the longersurfaces of the adhesive film when the adhesive film is pressed at 350°C. under 3 MPa for one minute.

Where the glass transition temperature is lower than 250° C. or thecoming-out length is greater than 1 mm in the present invention, thewater absorption rate is preferably not more than 3 wt. %, inparticular, 1.5 wt. %. The thinner the sealing material is or the higherthe percentage of the occupation of the adhesive in a package is, themore preferable it is to have a shorter coming-out length.

The adhesive according to the present invention can be formed of apolyimide or a polyamide alone. It is preferred to contain amide groupsfrom the standpoint of adhesion.

The term “amide groups” as used herein mean amide groups still remainingafter the ring closure for the formation of the polyimide. These amidegroups therefore do not include the amide groups in an amic acid as animide precursor.

Amide groups may mount to 10-90 mole %, preferably 20-70 mole %, morepreferably 30-50 mole % of the sum of imide groups and amide groups.Percentages smaller than 10 mole % lead to small adhesion butpercentages greater than 90 mole % result in a large water absorptionrate.

The heat-resistant adhesive according to the present invention can besynthesized principally from (A) a diamine or (A′) a diisocyanate and(B) an acid anhydride and/or (C) a dicarboxylic acid or an amide-formingderivative thereof. The heat-resistant adhesive can be easily producedby combining the above reactants and also adjusting their reactionratio, reaction conditions and molecular weight, optionally addingadditives while selecting their types and optionally adding anadditional resin such as an epoxy resin in such a way that the resultingheat-resistant adhesive has the prescribed properties described above,namely, a coming-out length of not more than 2 mm a water absorptionrate of not more than 3 wt. % and preferably a glass transitiontemperature of at least 200° C.

Examples of the diamine (A), which are usable in the present invention,include:

alkylenediamines such as hexamethylenediamine, octamethylenediamine anddodecamethylenediamine;

arylenediamines such as paraphenylenediamine, metaphenylenediamine and2,4-diaminotoluene;

diaminophenyl derivatives such as 4,4′-diaminodiphenyl ether (DDE),4,4′-diaminodiphenyl methane, 4,4′-diaminodiphenyl sulfone,3,3′-diaminodiphenyl sulfone, 4,4′-diaminobenzophenone,3,3′-diaminobenzophenone and 4,4′-diaminobenzanilide;

1,4-bis[1-(4-aminophenyl)-1-methylethyl]benzene (BAP);

1,3-bis[1-(4-aminophenyl)-1-methylethyl]benzene;

1,3-bis(3-aminophenoxy)benzene;

1,4-bis(3-aminophenoxy)benzene;

1,4-bis(4-aminophenoxy)benzene;

2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP);

2,2-bis[4-(3-aminophenoxy)phenyl]propane;

bis[4-(3-aminophenoxy)phenyl)] sulfone (m-APPS);

bis[4-(4-aminophenoxy)phenyl] sulfone; and

2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane.

Also usable as the diamine (A) in the present invention include, forexample, diamines represented by the following formula (1):.

wherein Y represents an amino group; R¹¹, R¹², R¹³ and R¹⁴ independentlyrepresent a C₁₋₄ alkyl or alkoxyl group, at least two of which areindependently an alkyl or alkoxyl group; and X is —CH₂—, —C(CH₃)₂—, —O—,—SO₂—, —CO— or —NHCO—.

Illustrative compounds represented by the formula (1) include:

4,4′-diamino-3,3′,5,5′-tetramethyldiphenylmethane,

4,4′-diamino-3,3′,5,5′-tetraethyldiphenylmethane,

4,4′-diamino-3,3′,5,5′-tetra(n-propyl)diphenylmethane,

4,4′-diamino-3,3′,5,5′-tetraisopropyldiphenylmethane,

4,4′-diamino-3,3′,5,5′-tetrabutyldiphenylmethane,

4,4′-diamino-3,3′-dimethyl-5,5′-diethyldiphenylmethane,

4,4′-diamino-3,3′-dimethyl-5,5′-diisopropyidiphenylmethane,

4,4′-diamino-3,3′-diethyl-5,5′-diisopropyldiphenylmethane,

4,4′-diamino-3,5-dimethyl-3′,5′-diethyldiphenylmethane,

4,4′-diamino-3,5-dimethyl-3′,5′-diisopropyldiphenylmethane,

4,4′-diamino-3,5-diethyl-3′,5′-diisopropyldiphenylmethane,

4,4′-diamino-3,5-diethyl-3′,5′-dibutyldiphenylmethane,

4,4′-diamino-3,5-diisopropyl-3′,5′-dibutyldiphenylmethane,

4,4′-diamino-3,3′-diisopropyl-5,5′-dibutyldiphenylmethane,

4,4′-diamino-3,3′-dimethyl-5,5′-dibutydiphenylmethane,

4,4′-diamino-3,3′-diethyl-5,5′-dibutyldiphenylmethane,

4,4′-diamino-3,3′-dimethyldiphenylmethane,

4,4′-diamino-3,3′-diethyldiphenylmethane,

4,4′-diamino-3,3′-di(n-propyl)diphenylmethane,

4,4′-diamino-3,3′-diisopropyldiphenylmethane,

4,4′-diamino-3,3′-dibutydiphenylmethane,

4,4′-diamino-3,3′,5-trimethyldphenyimethane,

4,4′-diamino-3,3′,5-triethyldiphenylmethane,

4,4′-diamino-3,3′,5-tri(n-propyl)diphenylmethane,

4,4′-diamino-3,3′,5-triisopropyldiphenylmethane,

4,4′-diamino-3,3′,5-tributyldiphenylmethane,

4,4′-diamino-3-methyl-3′-ethyldiphenylmethane,

4,4′-diamino-3-methyl-3′-isopropyldiphenylmethane,

4,4′-diamino-3-ethyl-3′-isopropyldiphenylmethane,

4,4′-diamino-3-ethyl-3′-butyldiphenylmethane,

4,4′-diamino-3-isopropyl-3′-butyldiphenylmethane,

2,2-bis(4-amino-3,5-dimethylphenyl)propane,

2,2-bis(4-amino-3,5-diethylphenyl)propane,

2,2-bis[4-amino-3,5-di(n-propyl)phenyl]propane,

2,2-bis(4-amino-3,5-dibutylphenyl)propane,

4,4′-diamino-3,3′,5′-tetramethyldiphenyl ether,

4,4′-diamino-3,3′,5,5′-tetraethyldiphenyl ether,

4,4′-diamino-3,3′,5,5′-tetra(n-propyl)diphenyl ether,

4,4′-diamino-3,3′,5,5′-tetraisopropyldiphenyl ether,

4,4′-diamino-3,3′,5,5′-tetrabutyldiphenyl ether,

4,4′-diamino-3,3′,5,5′-tetramethyldiphenyl sulfone,

4,4′-diamino-3,3′,5,5′-tetraethyldiphenyl sulfone,

4,4′-diamino-3,3′,5,5′-tetra(n-propyl)diphenyl sulfone,

4,4′-diamino-3,3′,5,5′-tetraisopropyldiphenyl sulfone,

4,4′-diamino-3,3′,5,5′-tetrabutyldiphenyl sulfone,

4,4′-diamino-3,3′,5,5′-tetramethyldiphenyl ketone,

4,4′-diamino-3,3′,5,5′-tetraethyldiphenyl ketone,

4,4′-diamino-3,3′,5,5′-tetra(n-propyl)diphenyl ketone,

4,4′-diamino-3,3′,5,5′-tetraisopropyldiphenyl ketone,

4,4′-diamino-3,3′,5,5′-tetrabutyldiphenyl ketone,

4,4′-diamino-3,3′,5,5′-tetramethylbenzanilide,

4,4′-diamino-3,3′,5,5′-tetraethylbenzanilide,

4,4′-diamino-3,3′,5,5′-tetra(n-propyl)benzanilide,

4,4′-diamino-3,3′,5,5′-tetraisopropylbenzanilide, and

4,4′-diamino-3,3′,5,5′-tetrabutylbenzanilide.

It is also possible to use, as the diamine (A), siloxydiaminesrepresented by the following formula (2):

wherein R¹⁵ and R¹⁸ each represents a divalent organic group, R¹⁶ andR¹⁷ each represents a monovalent organic group and m stands for aninteger of 1-100.

In the above formula (2), R¹⁵ and R¹⁸ may independently be atrimethylene group [—(CH₂)₃—], a tetramethylene group [—(CH₂)₄—], atoluylene group

or a phenylene group

while R¹⁶ and R¹⁷ may independently be a methyl, ethyl or phenyl group.Plural R¹⁶s and R¹⁷s can be either the same or different.

Where R¹⁵ and R¹⁸ each represents a trimethylene groups and R¹⁶ and R¹⁷each represents a methyl group in the formula (2), siloxane diamines inwhich m is 1, about 10 on average, about 20 on average, about 30 onaverage, about 50 on average and about 100 on average, respectively, areall commercially available from Shin-Etsu Chemical Co., Ltd. under thetrade names of “LP-7100”, “X-22-161AS”, “X-22-161A”, “X-22-161B”,“X-22-161C” and “X-22-161E”.

Examples of the diisocyanate (A′), which are usable in the presentinvention, include those similar to the above-exemplified diaminesexcept for the substitution of isocyanate groups for the amino groups.

Examples of the acid anhydride (B), which are usable in the presentinvention, include:

trimellitic anhydride,

pyromellitic dianhydride,

3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA),

3,3′,4,4′-biphenyltetracarboxylic dianhydride

2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride

bis(3,4-dicarboxyphenyl)ether dianhydride,

bis(3,4-dicarboxyphenyl)sulfone dianhydride,

4,4′-bis(3,4-dicarboxyphenoxy)diphenylsulfone dianhydride,

2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride,

ethylene glycol bistrimellitate dianhydride (EBTA),

decamethylene glycol bistrimellitate dianhydride (DBTA),

bisphenol A bistrimellitate dianhydride (BABT),

2,2-bis[4-(3,4-dicarboxybenzoyloxy)phenyl]hexafluoropropane dianhydride,

1,4-bis[1-methyl-1-{4-(3,4-dicarboxybenzoyloxy)-phenyl}ethyl]benzenedianhydride,

maleic anhydride,

methylmaleic anhydride,

nadic anhydride,

allyinadic anhydride

methyinadic anhydride

tetrahydrophthalic anhydride, and

methyltetrahydrophthalic anhydride.

Illustrative of the dicarboxylic acid, which are usable in the presentinvention, include terephthalic acid, isophthalic acid,biphenylcarboxylic acid, phthalic acid, naphthalenedicarboxylic acid anddiphenyletherdicarboxylic acid. Examples of the amide-formingderivatives of these dicarboxylic acids include dichlorides, dialkylesters and the like of the dicarboxylic acids exemplified above.

Further, the diamine (A) or the dicarboxylic acid (C) may partially bereplaced by an aminocarboxylic acid such as aminobenzoic acid.

Preferred examples of the diamine (A), which are usable for theprovision of the heat-resistant adhesives according to the presentinvention, include:

alkylene diamine,

metaphenylene diamine,

2,4-diaminotoluene,

4,4′-diaminodiphenyl ether (DDE),

4,4′-diaminodiphenyl methane,

4,4′-diaminodiphenyl sulfone,

3,3′-diaminodiphenyl sulfone,

3,3′-diaminobenzophenone,

1,3-bis(4-aminocumyl)benzene,

1,4-bis(4-aminocumyl)benzene,

1,3-bis(3-aminophenoxy)benzene,

1,4-bis(3-aminophenoxy)benzene,

1,4-bis(4-aminophenoxy)benzene,

2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP),

bis[4-(3-aminophenoxy)phenyl]sulfone (m-APPS),

bis[4-(4-aminophenoxy)phenyl]sulfone,

2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane,

4,4′-diamino-3,3′,5,5′-tetramethyldiphenylmethane,

4,4′-diamino-3,3′,5,5′-tetraethyldiphenylmethane,

4,4′-diamino-3,3′,5,5′-tetraisopropyldiphenylmethane,

4,4′-diamino-3,3′-dimethyl-5,5′-diethyldiphenylmethane,

4,4′-diamino-3,3′-dimethyl-5,5′-diisopropyldiphenylmethane,

4,4′-diamino-3,3′-diethyl-5,5′-diisopropyldiphenylmethane,

4,4′-diamino-3,3′-dimethyldiphenylmethane,

4,4′-diamino-3,3′-diethyldiphenylmethane, or

4,4′-diamino-3,3′-diisopropyldiphenylmethane.

In addition, it is also preferred to use commercially-available“LP-7100”, “X-22-161AS” and “X-22-161A” as the siloxanediamine of theformula (2).

Preferred examples of the acid anhydride (B) include:

trimellitic anhydride,

3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA),

2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride,

bis(3,4-dicarboxyphenyl)ether dianhydride,

bis(3,4-dicarboxyphenyl)sulfone dianhydride,

4,4′-bis(3,4-dicarboxyphenoxy)diphenylsulfone dianhydride,

2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride,

ethyleneglycolbistrimellitate dianhydride (EBTA),

decamethylene glycol bistrimellitate dianhydride (DBTA),

bisphenol A bistrimellitate dianhydride (BABT),

1,4-bis[1-methyl-1-{4-(3,4-dicarboxybenzoyloxy)-phenyl}ethyl]benzenedianhydride,

maleic anhydride,

nadic anhydride, and

allyinadic anhydride.

Incidentally, nadic anhydride has the following structural formula:

and allylnadic anhydride has the following structural formula:

When producing the resin by using the diamine (A), the acid anhydride(B) and the dicarboxylic acid (C), it is necessary to select and combinethese monomers so that the resulting resin preferably has Tg of 200° C.or higher, more preferably 250° C. or higher.

To obtain a heat-resistant adhesive having characteristics specified inthis invention, a polyimide and a polyamide may be mixed so that theresultant adhesive preferably has Tg of 200° C. or higher.

Without needing being limited to the polyimide and polyamide,polymaleimides and polyallylnadimides can also be employed likewise forthe production of heat-resistant adhesives of the present invention.

Polyimides can be obtained by thermal or chemical ring closure of thecorresponding polyamic acids. It is not necessary but desirable that thepolyimide used in this invention has been completely imidated.

The heat-resistant adhesive according to the present invention may becomposed of a polyimide or a polyamide alone or may be a mixtureobtained by combining the polyimide and the polyamide and, if necessary,an epoxy resin, a curing agent, a curing accelerator and/or the like.

In this case, it has been found that even if a heat-resistant adhesivehas Tg lower than 200° C., mixing of an additional resin such as anepoxy resin and one or more of the below-described additives, such as acoupling agent, make it possible to adjust its water absorption rate andcoming-out length within the respective ranges specified in the presentinvention.

No particular limitation is imposed on the epoxy resin which can bemixed with a specific heat-resistant polyimide adhesive of the presentinvention, in so far as it has at least 2 epoxy groups on average permolecule. Examples of such an epoxy resin include the glycidyl ether ofbisphenol A, the glycidyl ether of bisphenol F, phenolnovolak type epoxyresins, polyglycidyl esters of polyhydric alcohols, polyglycidyl estersof polybasic acids, alicylic epoxy resins and hydantoin epoxy resins.

In addition, fillers such as ceramic powder, glass powder, silver powderand copper powder and coupling agents can also be added to theheat-resistant adhesive of the present invention. The heat-resistantadhesive according to the present invention can also be used afterimpregnating it with a base sheet such as glass fabric, aramid fabricand carbon fiber fabric.

Usable examples of the coupling agent include:

vinylsilanes such as vinyltriethoxysilane, vinyltrimethoxysilane, andγ-methacryloxy propyltrimethoxysilane;

epoxysilanes such as γ-glycidoxypropyltrimethoxysilane,γ-glycidoxypropylmethyldiethoxysilane, andβ-(3,4-epoxycyclohexyl)ethyltrimethoxysilane;

aminosilanes such as γ-aminopropyltriethoxysilane,γ-aminopropyltrimehtoxysilane, andN-phenyl-γ-aminopropyltrimethoxysilane;

mercaptosilanes such as γ-mercaptopropyltrimethoxysilane; and

coupling agents such as titanates, aluminum chelates andzircoaluminates.

Of these, silane coupling agents are preferred with epoxysilane couplingagents being particularly preferred. Incidentallyγ-methacryloxypropyltrimethoxysilane has the following structuralformula:

whereas γ-glycidoxypropyltrimethoxysilane has the following structuralformula:

In the adhesive member, the heat-resistant adhesive according to thepresent invention can be used either alone, that is, by itself or bycoating it on a base film or impregnating a base sheet with it. When theheat-resistant adhesive is used alone, it can be coated directly on anobject to be bonded, such as a semiconductor chip or a lead frame, orcan be formed into a sheet-like form in advance, applied to the objectand then compression bonded on the object under heat.

The adhesive member comprising the adhesive of the present invention isformed in a shape and and imparted with properties suitable for bondingthe semiconductor chip to the lead frame in the manufacture of a sealedtype semiconductor package, especially an LOC semiconductor package.More specifically, the adhesive member employing the adhesive of thepresent invention has a shape and properties suitable for bondingbetween the semiconductor chip and the lead frame of the sealed typesemiconductor package having no tab where wire bonding for connectingthe semiconductor chip and the lead frame is made on the semiconductorchip.

When the heat-resistant adhesive according to the present invention isused as a composite adhesive sheet by coating it on a base film (orsheet), the composite adhesive sheet can be obtained by coating aheat-resistant adhesive having a water absorption rate of not more than3 wt. % and a coming-out length of not more than 2 mm and, preferably, aglass transition temperature of at least 200° C. or a varnish thereof onboth surfaces of a heat-resistant film, preferably a surface-treatedheat-resistant film.

The coating layer of each major surface of the heat-resistant film isformed by the same or different heat-resistant adhesive according to thepresent invention.

Examples of the heat-resistant film usable as the base film in thepresent invention include films of engineering plastics such aspolyimides, polyamides, polysulfones, polyphenylene sulfides,polyetheretherketones and polyarylates.

The heat-resistant film has a glass transition temperature (Tg) which ishigher than that (Tg) of the heat-resistant adhesive according to thepresent invention and is preferably at least 200° C., more preferably250° C. or higher. The heat-resistant film has a water absorption rateof not more than 3 wt. %, preferably 2 wt. % or lower.

Accordingly, the heat-resistant film employed in this invention maypreferably be a polyimide film in view of Tg, water absorption rate andcoefficient of thermal expansion. Particularly preferred is a filmequipped with the physical properties that the Tg is at least 250° C.,the water absorption rate is 2 wt. % or less and a coefficient ofthermal expansion of 3×10⁻⁵/° C. or lower.

To increase adhesion with the adhesive, it is desired to apply surfacetreatment to the heat-resistant film. Surface treatment methods includechemical surface treatment methods such as alkali treatment and silanecoupling treatment, physical treatment method such as sand blasting,plasma etching, and corona etching. Although they are all usable, it isdesired to choose and use a most suitable treatment method depending onthe adhesive. As surface treatment applied to a heat-resistant film uponapplication of the heat-resistant adhesive of this invention, chemicaltreatment or plasma etching is particularly preferred.

No particular limitation is imposed on the manner of coating theheat-resistant adhesive (varnish) on the heat-resistant film. Thecoating can be applied in any suitable manner by using, for example, adoctor blade, a knife coater, a die coater or the like. The film may becoated by feeding it through a varnish. This method is however notpreferred because it is difficult to control the thickness.

When the film coated with the heat-resistant adhesive of this inventionis subjected to heat treatment for the elimination of a solvent or forimidation, the temperature of the heat treatment varies depending onwhether the heat-resistant adhesive so coated is a varnish of a polyamicacid or a varnish of a polyimide.

In the case of the varnish of the polyamic acid, a temperature of Tg orhigher is needed to achieve imidation. In the case of the varnish of thepolyimide, no particular limitation is imposed insofar as it is highenough to eliminate the solvent. To improve the adhesion between theadhesive and the heat-resistant film, it is preferred to conduct theabove heat treatment at a temperature of 250° C. or higher.

The adhesive member making use of the heat-resistant adhesive accordingto the present invention is particularly effective for the bondingbetween a lead frame and a semiconductor chip.

When the adhesive according to the present invention is used for thebonding of the semiconductor chip and the lead frame, no particularlimitation is imposed on the manner of the bonding. This bonding can beachieved by a method most suited for each package so fabricated.

Various bonding methods can be used, including, for example:

(1) A composite sheet with a heat-resistant adhesive according to thepresent invention coated on opposite surfaces thereof is firstcompression-bonded onto a lead frame under heat. A semiconductor chip isthen compression-bonded under heat onto the heat-resistant adhesive ofthis invention on the opposite surface.

(2) A sheet with a heat-resistant adhesive according to the presentinvention coated on one surface thereof is first compression-bonded ontoa lead frame under heat. The opposite surface of the sheet is thencoated with the same adhesive or another adhesive according to thepresent invention, onto which a semiconductor chip iscompression-bonded.

(3) A film consisting of a heat-resistant adhesive of this inventionalone is held between a semiconductor chip and a lead frame and is thencompression-bonded under heat.

(4) A heat-resistant adhesive according to the present invention iscoated on a semiconductor chip or a lead frame and is compression-bondedwith a lead frame or a semiconductor chip.

Specific methods for bonding a semiconductor chip to a lead frame byusing an adhesive member making use of a heat-resistant adhesiveaccording to the present invention will be described with reference toFIGS. 1 to 3.

FIGS. 1 to 3 are schematic illustrations of the semiconductor packages,in which the shapes of the lead frames and the positions of thesemiconductor chips bonded on the lead frames are different. Eachsemiconductor package has been fabricated by bonding the semiconductorchip to the lead frame with the adhesive member making use of theheat-resistant adhesive according to the present invention and thenmolding the semiconductor chip and a bonded part between thesemiconductor chip and the lead frame with a molding compound.

In FIG. 1, the semiconductor is positioned below the lead frame.

In FIG. 2, the semiconductor is positioned above the lead frame.

In FIG. 3, the semiconductor is also positioned above the lead frame.

In FIGS. 1 to 3, there are shown the adhesive members at numeral 1, thesemiconductor chips at numeral 2, the lead frames at numeral 3, wires atnumeral 4 and the sealants at numeral 5.

The adhesive member making use of the heat-resistant adhesive accordingto the present invention are effective for bonding a semiconductor chipwith a lead frame so as to fabricate the semiconductor package in LOCstructure as illustrated in FIG. 1. The semiconductor package of LOCstructure is characterized by having a lead frame 3 and a semiconductorchip 2 which is connected to one of major surfaces (herein, called“lower surface”) of the lead frame 3 via an adhesive member 1, and inthat the other surface (herein, called “upper surface”) of the leadframe 3 and the semiconductor chip 2 are conductively connected via awire 4. The connecting position of the wire 4 and the lead frame 3 is inthe hypothetical shadow cast by projecting the semiconductor chip 2perpendicularly on the upper surface of the lead frame 3. The package ofLOC (lead on chip) structure as shown in FIG. 1 is different from theCOL (chip on lead) package of FIG. 2 and the package of FIG. 3 in thatthe rate of the volume occupied by the chip in the package is larger ascompared with those of the two others. This is because (1) the packageof FIG. 1 has not a tab while the package FIG. 3 has; and (2) the wirebonding is made above the chip in the package of FIG. 1, while it ismade on the surfaces of the chip in the packages of FIGS. 2 and 3, thussaving a space for the wire bonding in addition to the space where thechip is mounted. This increases the rate of the space occupied by thechip in the package of FIG. 1 and accordingly reduces the thickness ofthe sealing material, increasing the possibility of occurrence of thepackage cracks due to the adhesive, as compared with the packages ofFIGS. 2 and 3. Thus, an effective measure for reducing the possibilityof occurrence of the cracks has been provided. The adhesive of thepresent invention is especially effective for prevention or reduction ofoccurrence of the cracks in the package as shown in FIG. 1.

According to the following steps, a semiconductor package can bemanufactured.

In a case where the semiconductor package is fabricated by usingadhesive varnish, the varnish is first coated on an object. Then, asemiconductor chip is mounted on the film of the varnish after thecoated object is dried by heating at 100-300° C. for 1 second to 120minutes, preferably, at 150-250° C. for 5 seconds to 60 minutes.Thereafter, the semiconductor chip is pressed, while being heated, ontothe object under a condition at 200-500° C. under 0.01-10 MPa for 0.01seconds to 10 minutes, preferably, at 250-400° C. under 0.1-7 MPa for0.1-5 seconds, and then, the chip is wire-bonded, for example, with agold line. The wire bonding may be performed by supersonic wave, heatpressing or the both. The, a semiconductor package is obtained bymolding so as to cover the semiconductor chip.

In a case where an adhesive (single or complex) sheet is used, in orderto eliminate water contained in the adhesive sheet, the sheet is heatedin advance at 100-300° C. for 0.1-30 minutes, preferably, at 150-250° C.for 1-10 minutes, to effect preliminary drying. Next, the sheet is cutto a desired size. At this stage, the sheet may be stamped out with ametal mold or cut out by a cutter or the like. The next steps are heatpressing the adhesive sheet onto a bonding surface of a lead frame andheat pressing a bonding surface of a semiconductor chip onto theadhesive sheet. The heat pressing is performed under a condition at200-500° C. under 0.01-10 MPa for 0.1 seconds to 10 minutes, preferably,250-400° C. under 0.1-7 MPa for 0.1-5 seconds. After the adhesive sheetis heat pressed onto the bonding surface of the semiconductor chip, theadhesive sheet, which is bonded to the semiconductor chip, may be heatpressed onto the bonding surface of the lead frame. Finally, as in theabove described case of using adhesive varnish, a semiconductor packageis obtained by performing wire-bonding and molding.

Here, the wire-bonding is to conductably connect the semiconductor chipand a lead frame via a wire.

The above-mentioned molding can be performed with powdery moldingcompound using a metal mold, such as a transfer mold, or with liquidmolding compound using no metal mold.

In the present invention, the molding compound may be powdery or liquid,which may be thermosetting resin or thermoplastic resin.

In a case where the molding is performed with powdery molding compoundusing a metal mold, it is preferable to use a molding compound whosemain component is epoxy resin, under a condition at 140-200° C., for 30seconds to 3 minutes under 30-200 kg/cm².

In a case where the molding is performed with liquid molding compoundwithout a metal mold, it is preferable to use a molding compound whosemain component is epoxy resin, at room temperature to 150° C., for 30seconds to 1 hour.

Without being limited thereto the present invention, it can also beeffectively applied for the bonding of objects such as ceramic plates,metal plates, metal foils, plastic films, plastic plates and laminates.

Upon bonding each of such objects, the object can be bonded to anotherobject by coating the adhesive onto the first-mentioned object or wherethe adhesive is in the form of a sheet, interposing it between theobjects, heating the adhesive at a temperature equal to or higher to thesoftening point of the adhesive and then applying pressure.

The present invention will hereinafter be described specifically by thefollowing examples. It should however be borne in mind that thisinvention is by no means limited to or by the examples.

EXAMPLE 1

In a four-necked flask equipped with a stirrer, a thermometer, anitrogen inlet tube and a calcium chloride tube, 3.66 g (10 mmole) of4,4′-diamino-3,3′,5,5′-tetraisopropyldiphenylmethane (IPDDM) and 28.3 gof N,N-dimethylformamide (DMF) were charged and dissolved. While beingcooled below 5° C., the resulting solution was added with 5.76 g (10mmole) of bisphenol A bistrimellitate dianhydride (BABT) in portions.They were reacted for one hour under cooling below 5° C. and then for 6hours at room temperature, whereby a polyamic acid was synthesized. Tothe resultant reaction solution containing the polyamic acid, 2.55 g ofacetic anhydride and 1.98 g of pyridine were added, followed by reactionat room temperature for 3 hours, whereby a polyimide was synthesized.

The reaction solution containing the polyimide so obtained was pouredinto water and the resulting precipitate was collected, pulverized anddried, whereby the polyimide was obtained in the form of powder.

The polyimide powder so obtained was dissolved in DMF at a concentrationof 0.1 g/dl. The reduced viscosity of the polyimide solution as measuredat 30° C. was 0.71 dl/g.

In addition, a solubility test of the polyimide powder was conducted byadding it to various organic solvents to give a concentration of 5 wt. %and then observing its state of dissolution at room temperature. As aresult, the polyimide powder was found to be soluble in each of DMF,N-methylpyrrolidone (NMP), methylene chloride, dioxane, THF and toluene.

Further, the polyimide powder was dissolved in DMF. The varnish soobtained was cast onto a glass plate and dried at 100° C. for 10minutes. The resulting green film was peeled off from the glass plate,fixed on an iron frame and dried at 250° C. for one hour, whereby a filmwas obtained.

As a result of measurement of the glass transition temperature (Tg) ofthe thus-obtained polyimide film by the penetration method under a loadof 25 kg/cm² at a heating rate of 10° C./min, it was found to be 262° C.The heat decomposition temperature of the polyimide film was 405° C.

The film was immersed in water of 25° C. for 24 hours. As a result, itwas found to have a water absorption rate of 0.3 wt. %.

A 19×50 mm wide adhesive film of 25 μm in thickness was pressed at 350°C. under 3 MPa for one minute. The length of a came-out peripheralportion (hereinafter called “coming-out length” for the sake of brevity)of the adhesive as measured at a central part in the direction of thelonger surfaces of the adhesive film was found to be 0.8 mm.

In addition, a flexibility test was conducted by bending the polyimidefilm over an angle of 180°. The film developed no cracks, thus showinggood flexibility.

An NMP varnish of the polyimide was coated onto a film of “UPILEX S”(trade name; polyimide film; product of Ube Industries, Ltd.) which hadbeen plasma-etched, followed by drying at 100° C. for 10 minutes andthen at 300° C. for 10 minutes, whereby a composite sheet was obtained.The composite sheet so obtained was superposed on a 42 alloy (Fe—Nialloy whose nickel content is 42%) sheet, followed by pressing at 350°C. under 3 MPa for 5 seconds. As a result of measurement of the 90° peelstrength of the composite sheet, it was found to be 0.7 kN/m.

Using the composite sheet, a semiconductor chip of TSOP (thin smallout-line package) type was packaged as shown in FIG. 1. That is, thecomposite sheet is preliminarily dried by heating at 200° C. for oneminute, and then cut into a desired size. The sheet is mounted on a leadframe so as to be pressed at 375° C. under 3 MPa for one second. Next, asemiconductor chip is mounted on the sheet so as to be pressed at 400°C. under 3 MPa for 3 seconds. At last, using gold line, wire-bondingwith both supersonic and heat was performed, which is followed bymolding with epoxy forming material by transfer-mold method at 180° C.for 90 seconds under 70 kg/cm² and then holding at 180° C. for 5 hoursto be cured, so as to obtain a TSOP-type semiconductor package. Thepackage was subjected to moisturization for 48 hours at 85° C. and 85%RH and then immersed in a solder bath of 260° C. No cracks occurred.

EXAMPLE 2

In a similar manner to Example 1 except that 3.58 g (10 mmole) ofbis(3,4-dicarboxyphenyl)sulfone dianhydride (DSDA), 1.83 g (5 mmole) ofIPDDM and 2.05 g (5 mmole) of 2,2-bis[4-(4-aminophenoxy)phenyl]propane(BAPP) were used instead, a polyamic acid was obtained in the form ofvarnish. The varnish of the polyamic acid was treated as in Example 1,whereby a polyimide was obtained in the form of powder.

The polyimide so obtained was found to have a reduced viscosity of 1.21dl/g, Tg of 268° C., a thermal decomposition point of 410° C., a waterabsorption rate of 0.7 wt. % and a coming-out length of 0.01 mm.

In a similar manner to Example 1 except that the varnish of the polyamicacid was heat-treated at 100° C. for 10 minutes and then at 300° C. for15 minutes, a composite sheet was obtained. It was found to have anadhesive strength of 1.2 kN/m with a 42-alloy sheet. A semiconductorpackage of TSOP type obtained as in Example 1 developed no cracks whensoldered after moisturization.

EXAMPLE 3

In a similar manner to Example 1 except that 3.22 g (10 mmole) of3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BDTA) and 20.6 g ofNMP were used instead of BABT and DMF, respectively, a polyamic acid wasobtained in the form of varnish. Xylene (10 g) was added to the varnishso obtained, followed by heating at 180° C. for 5 hours, whereby apolyimide was obtained in the form of varnish.

The polyimide so obtained was found to have a reduced viscosity of 0.48dl/g, Tg of 300° C., a thermal decomposition temperature of 405° C., awater absorption rate of 1.0 wt. % and a coming-out length of 0.5 mm.

The polyimide varnish was coated onto a film of “KAPTON” (trade name;polyimide film; product of Du Pont-Toray Industries) which had beensubjected to silane coupling treatment after alkali treatment. The filmso coated was heat-treated at 100° C. for 10 minutes and then at 275° C.for 10 minutes, whereby a composite sheet was obtained. It was found tohave an adhesive strength of 0.92 kN/m with a 42-alloy sheet. Asemiconductor package of TSOP type obtained as in Example 1 developed nocracks when soldered after moisturization.

EXAMPLE 4

In a similar manner to Example 1 except that 5.76 g (10 mmole) of BABT,2.38 g (6.5 mmole) of IPDDM and 0.43 g (3.5 mmole) ofmetatoluylenediamine (MTDA) were used instead, a polyimide was obtainedin the form of powder.

The polyimide so obtained was found to have a reduced viscosity of 0.61dl/g, Tg of 275° C., a thermal decomposition temperature of 415° C., awater absorption rate of 0.5 wt. % and a coming-out length of 1.5 mm.

An NMP varnish of the polyimide was coated onto a “UPILEX S” film whichhad been subjected to alkali treatment, followed by drying at 100° C.for 10 minutes and then at 300° C. for 10 minutes, whereby a compositesheet was obtained. It was found to have an adhesive strength of 0.85kN/m with a 42-alloy sheet. The semiconductor package of SOJ (smalloutline J-leaded package type obtained as in Example 1 developed nocracks when soldered after moisturization.

EXAMPLE 5

In a similar manner to Example 3 except that 3.58 g (10 mmole) of DSDA,0.92 g (2.5 mmole) of IPDDM and 3.08 g (7.5 mmole) of BAPP were usedinstead, a polyimide was obtained in the form of powder.

The polyimide so obtained was found to have a reduced viscosity of 0.62dug, Tg of 255° C., a thermal decomposition temperature of 440° C., anda water absorption rate of 1.2 wt. % and a coming-out length of 0.2 mm.

DMAc varnish of the polyimide was coated onto a plasma-etched film of“UPILEX S”, followed by drying at 100° C. for 10 minutes and then at250° C. for 10 minutes, whereby a composite sheet was obtained. It wasfound to have an adhesion strength of 1.40 kN/m with a 42-alloy sheet.The semiconductor package of TSOP type obtained as in Example 1developed no cracks when soldered after moisturization.

EXAMPLE 6

In 24.5 g of DMF, 4.10 g (10 mmole) of BAPP were dissolved, followed bythe addition of 2.02 g (20 mmole) of triethylamine. While being cooledbelow 5° C., the resulting solution was added with 2.03 g (10 mmole) ofisophthaloyl chloride in portions. They were reacted for 5 hours below5° C. As in Example 1, a polyamide was obtained in the form of powder.

The polyamide so obtained was found to have a reduced viscosity of 0.45dl/g, Tg of 219° C., a thermal decomposition temperature of 425° C., awater absorption rate of 2.3 wt. % and a coming-out length of 2.4 mm.

A DMF varnish with 85 wt. % of a polyimide obtained as in Example 1 and15 wt. % of the polyamide obtained in this Example mixed therein wascoated onto a plasma-etched film of “UPILEX S”, followed by drying at100° C. for 10 minutes and then at 250° C. for 10 minutes, whereby acomposite sheet was obtained. The composite sheet so obtained wassuperposed on a 42 alloy sheet, followed by pressing at 350° C. under 3MPa for 5 seconds. As a result of measurement of the 90° peel strengthof the sheet, it was found to be 1.2 kN/m.

The composite film was found to have Tg of 255° C., a water absorptionrate of 0.6 wt. % and a coming-out length of 1.5 mm.

Using the composite sheet, a semiconductor chip of SOJ type was packagedas shown in FIG. 1. The film was subjected to moisturization for 48hours at 85° C. and 85% RH and then immersed in a solder bath of 260° C.No cracks were occurred.

EXAMPLE 7

In 20 g of DMF, 1.74 g (7 mmole) g of 4,4′-diaminodiphenylsulfone (DDS)and 1.23 g (3 mmole) of BAPP were dissolved, followed by the addition of2.02 g (20 mmole) of triethylamine. While being cooled below 5° C., theresulting solution was added with 2.03 g (10 mmole) of isophthaloylchloride in portions. They were reacted for 5 hours below 5° C. As inExample 1, a polyamide was obtained in the form of powder. The polyamideso obtained was found to have a reduced viscosity of 0.88 dl/g, Tg of260° C., a thermal decomposition temperature of 435° C., a waterabsorption rate of 2.5 wt. % and a coming-out length of 0.2 mm.

Using an NMP varnish with 60 wt. % of the polyimide obtained as inExample 1 and 40 wt. % of the polyamide obtained in this Example mixedtherein, a composite sheet was obtained in a similar manner toExample 1. The adhesive strength of the composite sheet so obtained witha 42 alloy sheet was found to be 1.6 kN/m.

The composite film was found to have Tg of 260° C., a water absorptionrate of 1.1 wt. % and a coming-out length of 0.5 mm.

Using the composite sheet, a semiconductor chip of TSOP type waspackaged as in Example 1. The package developed no cracks when solderedsubsequent to moisturization.

EXAMPLE 8

In a similar manner to Example 6 except that 1.83 g (5 mmole) of IPDDM,2.05 g (5 mmole) of BAPP, 0.64 g (3 mmole) of4-chloroformylbenzene-1,2-dicarboxylic anhydride, 0.30 g (3 mmole) oftriethylamine and 30 g of NMP were used instead, a polyamic acid wasobtained in the form of varnish. The varnish so obtained was added with2.51 g (7 mmole) of bis(3,4-dicarboxyphenyl)sulfone dianhydride (DSDA)in portions below 5° C., followed by reaction below 5° C. for 5 hours.Acetic anhydride and pyridine were thereafter added to the reactionmixture. Following the procedures described in Example 1, apolyamide-imide was obtained in the form of powder.

The polyamide-imide so obtained was found to have a reduced viscosity of1.15 dl/g, Tg of 258° C., a thermal decomposition temperature of 385°C., a water absorption rate of 1.0 wt. % and a coming-out length of 0.02mm.

A DMAc varnish of the polyamide-imide was coated onto a “KAPTON” filmwhich had been subjected to silane coupling treatment after alkalitreatment. The film so coated was heat-treated at 100° C. for 10 minutesand then at 275° C. for 10 minutes, whereby a composite sheet wasobtained. It was found to have an adhesive strength of 1.4 kN/m with a42-alloy sheet. A semiconductor package of TSOP type obtained as inExample 1 developed no cracks when soldered after moisturization.

EXAMPLE 9

In a similar manner to Example 1 except that 5.76 g (10 mmole) of BABT,2.74 9 (7.5 mmole) of IPDDM, 0.41 g (1.0 mmole) of BAPP and 1.26 g (1.5mmole) of “X-22-161AS” were used instead, a polyimide was obtained inthe form of powder. The polyimide so obtained was found to have areduced viscosity of 0.65 dl/g, Tg of 226° C., a thermal decompositiontemperature of 396° C., a water absorption rate of 0.3 wt. % and acoming-out length of 1.7 mm.

An NMP varnish of the polyimide so obtained was coated onto aplasma-etched film of “UPILEX S”, followed by drying at 100° C. for 10minutes and then at 300° C. for 10 minutes, whereby a composite sheetwas obtained. The composite sheet so obtained was found to have anadhesive strength of 0.80 kN/m. A semiconductor package of SOJ typeobtained as in Example 1 developed no cracks when soldered aftermoisturization.

EXAMPLE 10

In a similar manner to Example 1 except that 3.58 g (10 mmole) of DSDAand 4.32 g (10 mmole) of bis[4-(4-aminophenoxy)phenyl]sulfone were usedinstead, a polyimide was obtained in the form of powder.

The polyimide so obtained was found to have a reduced viscosity of 0.87dl/g, Tg of 270° C., a thermal decomposition temperature of 520° C., awater absorption rate of 2.3 wt. % and a coming-out length of 0.01 mm.

An NMP varnish of the polyimide so obtained was coated onto aplasma-etched film of “UPILEX S”, followed by drying at 100° C. for 10minutes and then at 300° C. for 10 minutes, whereby a composite sheetwas obtained. The composite sheet so obtained was found to have anadhesive strength of 1.0 kN/m. A semiconductor package of TSOP typeobtained as in Example 1 developed no cracks when soldered aftermoisturization.

EXAMPLE 11

As in Example 1, a film composed of an adhesive alone was formed usingthe polyimide of Example 2. A semiconductor package of TSOP typeobtained using the so-formed film in a similar manner to Example 1developed no cracks when soldered after moisturization.

EXAMPLE 12

An adhesive layer was formed on a semiconductor chip by using an NMPvarnish of the polyamide-imide which had been obtained in Example 8. Asemiconductor package of TSOP type formed as shown in FIG. 1 by usingthe chip with the adhesive layer thereon developed no cracks even whenit was soldered after moisturization as in Example 1.

EXAMPLE 13

In 23.0 g of NMP, 2.87 g (7 mmole) of BAPP and 0.75 g (3 mmole) of“LP-7100” were dissolved. While being cooled below 5° C., the resultingsolution was added with 2.13 g (10 mmole) of4-chloroformylbenzene-1,2-dicarboxylic anhydride in portions. To theresulting mixture, 2.02 g (20 mmole) of triethyl amine were added,followed by the reaction for 5 hours below 5° C. As in Example 1, apolyamide-imide was obtained in the form of powder.

The polyamide-imide so obtained was found to have a reduced viscosity of0.57 dl/g, Tg of 185° C., a thermal decomposition temperature of 420°C., a water absorption rate of 0.13 wt. % and a coming-out length of 0.8mm.

A varnish which had been obtained by dissolving 100 g of thepolyamide-imide powder and 3 g of γ-glycidoxypropyltrimethoxysilane in400 g of DMF was coated on one surface of a polyimide film (“UPILEX S”,trade name), followed by drying at 100° C. for 10 minutes. The othersurface of the polyimide film was also coated with the varnishsimilarly, followed by drying at 250° C. for 10 minutes, whereby acomposite sheet was obtained. The composite sheet so obtained was foundto have an adhesive strength of 1.6 kN/m with a 42 alloy sheet. Theadhesive layers were found to have Tg of 185° C., a water absorptionrate of 1.3 wt. % and a coming-out length of 0.2 mm.

First, the composite sheet was pressed and adhered to a lead frame at350° C. under 6 MPa for 3 seconds and then a chip was pressed andadhered to the other side of the sheet at 375° C. under 6 MPa for 3seconds. After wire bonding, the resulting wired chip was molded withepoxy forming material, as a sealant, by transfer-mold method at 180° C.for 90 seconds under 70 kg/cm² and then held at 180° C. for 5 hours tobe cured. The TSOP-type-package so obtained was subjected tomoisturization at 85° C. and 85% RH for 48 hours, and solder was thencaused to reflow in a infrared oven controlled at 245° C. No cracks weredeveloped.

EXAMPLE 14

In 34.7 g of NMP, 3.69 g (9 mmole) of BAPP and 0.88 g (1 mmole) ofX-22-161AS were dissolved. Below 5° C., 4.10 g (10 mmole) ofethyleneglycolbistrimellitate dianhydride were thereafter added to theresulting solution in portions, followed by the reaction for 2 hours. Tothe reaction mixture, 15 g of xylene were added. The resulting mixturewas reacted at 180° C. for 5 hours under a nitrogen gas stream whilecondensed water was azeotropically removed together with xylene, wherebya polyimide was synthesized. The reaction mixture containing thepolyimide so synthesized was poured into water and the resultingprecipitate was collected, pulverized and dried, whereby the polyimidewas obtained in the form of powder.

The polyimide so obtained was found to have a reduced viscosity of 0.65dl/g, Tg of 170° C., a thermal decomposition temperature of 390° C., awater absorption rate of 1.0 wt. % and a coming-out length of 1.8 mm.

Using a varnish obtained by dissolving 100 g of the polyimide powder and5 g of γ-glycidoxypropyl-methyldiethoxysilane in 400 g of DMF, acomposite sheet was obtained as in Example 13. The composite sheet hadan adhesive strength of 1.3 kN/m with a 42 alloy sheet. In addition, theadhesive layers were found to have Tg of 172° C., a water absorptionrate of 1.0 wt. % and a coming-out length of 1.8 mm.

A semiconductor package of SOJ type obtained as in Example 13 developedno cracks when soldered after moisturization.

EXAMPLE 15

In a similar manner to Example 13 except that 3.28 g (8 mmole) of BAPP,0.40 g (2 mmole) of dodecamethylenediamine and 2.13 g (10 mmole) of4-chloroformylbenzene-1,2-dicarboxylic anhydride, a polyamide-imide wasobtained in the form of powder.

The polyamide-imide so obtained was found to have a reduced viscosity of0.85 dl/g, Tg of 190° C., a thermal decomposition temperature of 395°C., a water absorption rate of 0.1 wt. % and a coming-out length of 0.6mm.

A varnish obtained by dissolving 100 g of the polyamide-imide powder and10 g of γ-glycidoxypropyl-methyldiethoxysilane in 400 g of NMP wascoated on both surfaces of a polyimide film (“UPILEX S”, trade name).The varnish so coated was dried at 100° C. for 10 minutes and then at275° C. for 10 minutes, whereby a composite sheet was obtained. Thecomposite sheet was found to have an adhesive strength of 1.4 kN/m witha 42 alloy sheet. In addition, the adhesive layers were found to have Tgof 191° C., a water absorption rate of 1.1 wt. % and a coming-out lengthof 0.2 mm.

A semiconductor package of TSOP type obtained as in Example 13 developedno cracks when soldered after moisturization.

COMPARATIVE EXAMPLE 1

Using a DMF varnish of the polyamide obtained in Example 6, a compositesheet was obtained in a similar manner to Example 1. The adhesivestrength of the sheet with 42 alloy sheet was found to be 1.60 kN/m. Asemiconductor package of TSOP type obtained as in Example 1 developedcracks when soldered after moisturization.

COMPARATIVE EXAMPLE 2

In 20 g of DMF, 2.11 g (8.5 mmole) of DDS and 0.62 g (1.5 mmole) of BAPPwere dissolved, followed by the addition of 2.02 g (20 mmole) oftriethylamine. While being cooled below 5° C., the resulting mixture wasadded with 2.03 g (10 mmole) of isophthaloyl chloride in portions. Theywere reacted below 5° C. for 5 hours. In a similar manner to Example 1,a polyamide was obtained in the form of powder.

The polyamide so obtained was found to have a reduced viscosity of 0.45dl/g, Tg of 280° C., a thermal decomposition temperature of 430° C., awater absorption rate of 3.5 wt. % and a coming-out length of 1.2 mm.

A varnish of the above polyamide was coated onto a “KAPTON” film whichhad been subjected to silane coupling treatment after alkali treatment.The film so coated was heat-treated at 100° C. for 10 minutes and thenat 250° C. for 10 minutes, whereby a composite sheet was obtained. Itwas found to have an adhesion strength of 1.5 kN/m with a 42-alloysheet. A semiconductor package of TSOP type obtained as in Example 1developed cracks when soldered after moisturization.

COMPARATIVE EXAMPLE 3

In a similar manner to Example 4, polyimide powder having a reducedviscosity of 0.35 dl/g was obtained. The polyimide so obtained was foundto have Tg of 275° C., a thermal decomposition temperature of 410° C., awater absorption rate of 0.6 wt. % and a coming-out length of 3.4 mm.

The composite sheet obtained following the procedures described inExample 4 was found to have an adhesive strength of 0.9 kN/m with a42-alloy sheet. A semiconductor package of SOJ type obtained as inExample 1 developed cracks when soldered after moisturization.

COMPARATIVE EXAMPLE 4

In a similar manner to Example 1 except that 4.10 g (10 mmole) ofethyleneglycolbistrimellitate dianhydride and 4.32 g (10 mmole) ofbis[4-(3-aminophenoxy)phenyl]sulfone instead, a polyimide was obtainedin the form of powder.

The polyimide so obtained was found to have a reduced viscosity of 0.44dl/g, Tg of 187° C., a thermal decomposition temperature of 465° C., awater absorption rate of 1.1 wt. % and a coming-out length of 2.2 mm.

A semiconductor package of TSOP type obtained as in Example 1 developedcracks when soldered after moisturization. Those results are shown inTable 1.

TABLE 1 (1) Composition of adhesive Reduced Water Coming-out Acidcomponent/amine viscosity Tg absorption length component = 10/10 (dl/g)(° C.) rate (wt. %) (mm) Cracks Ex. 1 BABT/IPDDM 0.71 262 0.3 0.8 Notobserved at 260° C. Ex. 2 DSDA/IPDDM 5 1.21 268 0.7 0.01 Not BAPP 5observed at 260° C. Ex. 3 BTDA/IPDDM 0.48 300 1.0 0.5 Not observed at260° C. Ex. 4 BABT/IPDDM 6.5 0.61 275 0.5 1.5 Not MTDA 3.5 observed at260° C. Ex. 5 DSDA/IPDDM 2.5 0.62 255 1.2 0.2 Not BAPP 7.5 observed at260° C. Ex. 6 (1) IP/BAPP 0.45 219 2.3 2.4 Not Polyimide of Ex. 1 85 wt.% — 255 0.6 1.5 observed Polyamide of (1) 15 wt. % at 260° C.

TABLE 1 (2) Composition of adhesive Reduced Water Coming-out Acidcomponent/amine viscosity Tg absorption length component = 10/10 (dl/g)(° C.) rate (wt. %) (mm) Cracks Ex. 7 (2) IP/DDS 7 0.88 260 2.5 0.2 NotBAPP 3 observed Polyimide of Ex. 1 60 wt. % — 260 1.1 0.5 at 260° C.Polyamide of (2) 40 wt. % Ex. 8 TA 3/IPDDM 5 1.15 258 1.0 0.02 Not DSDA7/BAPP 5 observed at 260° C. Ex. 9 BABT/IPDDM 7.5 0.65 226 0.3 1.7 NotBAPP 1.0 observed “161AS” 1.5 at 260° C. Ex. 10 DSDA/p-APPS 0.87 270 2.30.01 Not observed at 260° C. Ex. 11 A film composed 1.21 268 0.7 0.01Not of polyimide observed of Ex. 2 alone at 260° C. Ex. 12 Apolyamide-imide 1.15 258 1.0 0.02 Not of Ex. 8 coated observed on a chipat 260° C.

TABLE 1 (3) Composition of adhesive Reduced Water Coming-out Acidcomponent/amine viscosity Tg absorption length component = 10/10 (dl/g)(° C.) rate (wt. %) (mm) Cracks Comp. Polyamide (1) of Ex. 6 0.45 2192.3 2.4 Observed Ex. 1 at 260° C. Comp. IP/DDS 8.5 0.45 280 3.5 1.2Observed Ex. 2 BAPP 1.5 at 260° C. Comp. BABT/IPDDM 6.5 0.35 275 0.6 3.4Observed Ex. 3 MTDA 3.5 at 260° C. Comp. EBTA/m-APPS 0.44 187 1.1 2.2Observed Ex. 4 at 260° C. Ex. 13 (3) TA/BAPP 7 0.57 185 1.3 0.8 Not“LP-7100” 3 observed Polyimide of (3) 100 wt. % — 185 1.3 0.2 at 245° C.τ-GPTM  3 wt. %

TABLE 1 (4) Composition of adhesive Reduced Water Coming-out Acidcomponent/amine viscosity Tg absorption length component = 10/10 (dl/g)(° C.) rate (wt. %) (mm) Cracks Ex. 14 (4) EBTA/BAPP 9 0.65 170 1.0 1.8Not “161AS” 1 observed Polyimide of (4) 100 wt. % — 172 1.0 1.0 at 245°C. τ-GPME  5 wt. % Ex. 15 (5) TA/BAPP 8 0.85 190 1.0 0.6 Not DDMA 2observed Polyimide of (5) 100 wt. % — 191 1.1 0.2 at 245° C. τ-GPTM  10wt. %

IP: Isophthalic acid

TA: Trimellitic anhydride

“LP-7100”: Siloxyamine; trade name; product of Shin-Etsu Chemical Co.,Ltd.

IPDDM: 4,4′-Diamino-3,3′,5,5′-tetraisopropyldiphenylmethane

DDS: 4,4′-Diaminodiphenylsulfone

BTDA: 3,3′,4,4′-benzophenonetetracarboxylic dianhydride

BAPP: 2,2-bis[4-(4-aminophenoxy)phenyl]propane

DSDA: Bis[3,4-dicarboxyphenyl]sulfone dianhydride

“161AS”: “X-22-161AS”: siloxyamine; trade name; product of Shin-EtsuChemical Co., Ltd.

p-APPS: Bis[4-(4-aminophenoxy)phenyl]sulfone

m-APPS: Bis[4-(3-aminophenoxy)phenyl]sulfone

EBTA: Ethyleneglycolbistrimellitate dianhydride

DDMA: Dodecamethylenediamine

γ-GPTM: γ-Glycidoxypropyltrimethoxysilane

γ-GPME: γ-Glycidoxypropylmethyldiethoxysilane

What is claimed is:
 1. A fabrication process of a semiconductor package,comprising the steps of: (1) bonding a semiconductor chip to a firstside of two substrates of a lead frame with an adhesive member; (2)conductivelv connecting a second side of said two surfaces of said leadframe and said semiconductor chip via a wire; and (3) molding a moldingcompound so that the molding compound covers at least said semiconductorchip and a bonded part between the semiconductor chip and said frame,wherein said wire and said lead frame are connected at a position insidea shadow which is formed by projecting said semiconductor chipvertically on said second side of said lead frame; and said adhesivemember is a composite adhesive sheet comprising a heat-resistant filmand a coating layer of an adhesive applied on both major surfaces of theheat resistant film; and said adhesive member is made of polyimide orpolyamide and includes a heat-resistant adhesive having a coming-outlength of not more than 2 mm and a water absorption rate of not morethan 3 wt. % wherein the coming-out length of said adhesive is measuredby the steps of pressing a film of said adhesive having a size of 19mm×50 mm with a thickness of 25 μm at 350° C. under 3 Mpa for oneminute; and measuring a coming-out length of said adhesive at a centralpart in the direction of the longer surface of said adhesive film.
 2. Afabrication process of a semiconductor package as defined in claim 1,wherein the glass transition temperature of said heat-resistant adhesiveis 200° C. or higher.
 3. A fabrication process of a semiconductorpackage as defined in claim 1, wherein the adhesive applied in the formof the coating layer on one of said major surfaces of saidheat-resistant film comprises a heat-resistant adhesive which isdifferent from the adhesive applied in the form of the coating layer onthe other of said major surfaces of the heat-resistant film.
 4. Afabrication process of a semiconductor package as defined in claim 1,wherein the adhesive applied in the form of the coating layer on one ofsaid major surfaces of said heat-resistant film comprises aheat-resistant adhesive which is the same as the adhesive applied in theform of the coating layer on the other of said major surfaces of theheat-resistant film.
 5. A fabrication process of a semiconductor packageas defined in claim 1, wherein the glass transition temperature of saidheat-resistant film is higher than the glass transition temperature ofsaid heat-resistant adhesive.
 6. A fabrication process of asemiconductor package as defined in claim 1, wherein the glasstransition temperature of said heat-resistant adhesive is 200° C. orhigher.
 7. A fabrication process of a semiconductor package as definedin claim 2, wherein the adhesive applied in the form of the coatinglayer on one of said major surfaces of the heat-resistant film comprisesa heat-resistant adhesive which is different from the heat-resistantadhesive applied in the form of the coating layer on the other of saidmajor surfaces of the heat-resistant film.
 8. A fabrication process of asemiconductor package as defined in claim 7, wherein the glasstransition temperature of said heat-resistant film is higher than theglass transition temperature of said heat-resistant adhesive.
 9. Afabrication process of a semiconductor package as defined in claim 2,wherein the adhesive applied in the form of the coating layer on one ofsaid major surfaces of said heat-resistant film comprises aheat-resistant adhesive which is the same as the adhesive applied in theform of the coating layer on the other of said major surfaces of theheat-resistant film.
 10. A fabrication process of a semiconductorpackage as defined in claim 9, wherein the glass transition temperatureof said heat-resistant film is higher than the glass transitiontemperature of said heat-resistant adhesive.
 11. A fabrication processof a semiconductor package as defined in claim 3, wherein the glasstransition temperature of said heat-resistant film is higher than theglass transition temperature of said heat-resistant adhesive.
 12. Afabrication process of a semiconductor package as defined in claim 4,wherein the glass transition temperature of said heat-resistant film ishigher than the glass transition temperature of said heat-resistantadhesive.
 13. A fabrication process of a semiconductor package accordingto claim 1, wherein said step (3) is a step of molding said moldingcompound in a manner that the molding compound covers the bonded partwhere said semiconductor chip is bonded to said lead frame, and anentire surface of said semiconductor chip.